1. Field of the Invention
The present invention relates generally to an apparatus for depositing granules on a moving sheet. More particularly, this invention relates to an apparatus having a perforated belt which travels transversely with respect to a moving sheet upon which the granules are deposited through holes in the belt. The invention is especially useful in making roofing sheets or shingles.
2. Description of the Prior Art
For many years roofing sheets and shingles have been made by depositing slate granules on a sheet of organic or glass fiber material which has been impregnated with asphalt and has a coating of asphalt into which the granules become embedded. The granules serve as weather resistant elements to protect the underlying sheet and also to provide a degree of fire protection.
The apparatus for making the sheet is conventional, as is also the apparatus for impregnating and coating the sheet with asphalt. Prior to the invention, the slate granules have been deposited on the molten asphalt coating from a large hopper having an elongated slot in its lower edge. The granules flow through the slot onto the upper surface of the sheet. Various devices may be used to control the flow of the granules.
Although the conventional apparatus has been used for many years, it is not completely satisfactory in that it does not provide an easy adjustment of the flow of granules. Furthermore, the control devices on the hopper are large, cumbersome and at times difficult to adjust and keep clean.
It is desirable that a granule depositing device be provided which overcomes many of the shortcomings of the prior art hopper discharge control apparatus.